Tube extruding die and method



Sept. 27, 1949. H. F. TEMPLE 2,483,376

TUBE EXTRUDING DIE AND METHOD Filed Nov. 27, 1959 INVENTOR Patented Sept. 27? 1949 ,mener aerei-fos Aflnszgsie Y v"TUBE EXERUDIN G DIE AND METHOD Harold AF. Vcmple, Freeport, eN. XV., :SSliglmr; to `Vietorlvletal Products Corporatiomomokl'yn,

Y., a corporation .of NewiXolf'k This invention related-to impactextrusionapparatus zand -prdcesses vwhereby thin -Walled .hollowarticlesiareormedifrom va .discof extrudable metakbymeansiof la, sudden pressure. or blow .,01,

nl otherl-words, by impactaeXtrus-ion. 5

;Thinf.walled eylindrieall tubes such as-c Ollapsible tubesfliorfthe reception oi pastmaterial. have heretofore Vlbeennomade by -the impact extrusion method wherein-a Adisc. or. slug .of1non-errous'ex- Vtrudable:metalzsuchiast,tin,-faluminium,lead,; zinc .10

`or allnys AYtheneof lhaye been .suddenly lpressed lor Jstruclstfwith vertically reciprocatingplungenor male ,die latter. Ethe .disc f has been inserted inne. suitablyshapedfemale die. The eXcess-metaliof outofftheemalefdm and aroundthe plunger. Its eylindrical shape isi determined by E .the seyln- Ldrical, shapeff the.elpnirig of :thedemaladeiand the cylindrical shape of thallowernd .of-themale diecorgplunger. determined .by the difference :between the 4diameters-of .the;,de land-:the plunger. l'hefshapeyof thentube bottomrmay bet greatly vgariedfiheingtentire1y;die:ormed .within .1 the female dien-.by the .plunger as contrasted-:With theaormaton-lolthe `remainriier .orfbodyfsthettube Vby v extrlusion.

insofar4 asll am gamelle; no attempt.;hasl-.hereton ioregdeeenrmade, ether than :shapingtthe female jd-ie,to rcontroleorinterfere'.with ,the ,bow ofi-,the metal o utoftherfemale;diesdurngltheiextremely smallinterval; oi;timeeduring..:whichtthe impact extrusion operatienetakes place. The-:shapeeof rtheiresultinrg,:tube has :thereore,=.been determined Thethicknessnof-.fthe ,tube-Wall is .20

maylalsolbeeneatlymaried andltheetuheprovided with-1mmopenings,meclisi-lembpssieg .orgthellike as un .ordinaryfdieipressneseparations, the eX.-V .trudeditubeipart. orlbedy:beingiormed .-ttQgether .withzits'f dieipressedlpartfall .,inwaesegleg operation Afreiem-a ,suitableslugf ondisc.

Myainnentionetherefore Gontemplatesfthepreylsion ofealmethedrofecontrolliegarldldiyertng Lthe metal lowinle eut-mf ,aifemale die: durlngan impatti.extrusioneperationfwherebygtubestreans, shells; and ether@ like; of lmul-tiple ,diameter and l.ol Winniedficrosseseotionlaliishapesglandvof allyisuitalole .innere and ,outer eenauratien at :its ftd-ieg l pressed flowenendmaylbelormedfmaaasingleleperationand Efmmranxtrudable :slug- ;timeinvention;flirtherfeontemplateslthe fnrovi.-

heretofore =solely..by the-shapeeof tithe '.epeningiin -35 @Bpl/iedv,the `Vfemal. idle. Land .the corresponding slightly smaller sliepenf the cooperating.ieXtreme:or..A low- .ermost endzzof; the plunger.

All', :have `found, however, @that after Athe,urn-:tal

Ai'ows upwardly out .ofthe` female idie. tozbeginzthe 40 iormationeof a tube, theadrection; of ztheowof the metal :may be controlled and Variedptofasubstantial extent AlimitedV only lby l the `,duct-1111151..10f the metal :used whereby l it zbecomes.. possible-ato greatly ,vary the; shape of .the extruded part sor body .of :.the -resulting tube from the cylindrical shape heretoforeA in generalv use. ,Italso becomes possibleY to change ,the diameters of selected; parts ,of the length :of therresulting :tube @byrduertng the metal flowing-aloha` the;.pl11ngerf into; ay difierent-r .direction andft further becomes ,possible-to change'tl'le` cross-sectional` shape and; size; of Jthe tubelatfvariousparts of-its-length- =.-Eurthermore, by hanging. the shape.. oi thef cooperatingg parts gef the-die, the Shapefmesottomenuoflthetube 5 .l Eg..-;2 .fnartialzfsecton :arxdzfront elevation ofitheesamel-nthe nesitien whereimtheeextnuuinggonerationrhaseenzeompletedato ormr attube hayl'xgfdierent fmultipleediameters.

lFig;J3 lis aneelevationalwiew "partlylinl section ettsupplementaryl. means-forrperforniingla typieal .trimrating.I and I forming-1. operationuponA avea-mer tube extruded in accordance -with-myinvention and ertthejpurposeeof "nishingthe' tube *orne/n.

i 4;'is "a fragmentary vertical 'section oi '.a mode'd form f theidies.. employed 'ffor the bpur.- posefiorming amener; ,end' tube, candorfshell. ".;Eig.;5, is* a. top;l plan tView oi amodied. ormf theplungenonmaledie employed mathe-purpose ofl-extnuding tubes :cans 4;or,slf=1ells .withvabeaded wall Surfacelfortpartf oflits length.

Fig. l 6 is a asimilar Tnew oftanother ymodied form ofethemaleldienrlplunger empleyedlfortthe purnesesofeezgtrudmg:hollewartielesfhayinglpart 3 of the length thereof expanded into hexagonal form.

Fig. 7 is a similar view of the same showing the means employed for extruding a hollow article in which the lower cylindrical part is expanded into an upper hexagonal part and in which the lower end part of the article is die-formed into any desired shape such as conical.

Fig. 8 is a similar view of the dies showing the means employed for extruding a hollow article in part hexagonal in cross-section and in part crcular in cross-section.

In the practical embodiment of the invention shown by way of example, the male die l is substantially of the usual construction being provided with the passage Il for compressed air which is intended to operate the air valve l2 to discharge the article extruded upon the plunger or male die. In the lorm of the invention shown, the male die lil is of the usual cylindrical shape and is reciprocated by suitable means well known in the art to enter and to leave the female die I3 and to compress the slug ll therein. The die cavity ill of said female die is, as is customary, also of generally cylindrical .shape but in this case is provided with a substantially closed bottom wall I5 for the production of tubes, cans, shells, casings, or the like hollow articles having a closed bottom as i6 (Fig. 2).

known in the art after which the plunger is moved down with considerable force against the slug thus compressing the slug within the die cavity.

The slug or disc l is inserted into the female die by mechanism well The lower end I8 o the plunger cooperates with Y the wall of the die cavity to form the lower end of the tube into the exact inner and outer shapes desired while at the same time, the excess material is suddenly forced out of the die cavity and .squirts or ows upwardly therefrom around the plunger to form a thin-walled tube, having in the instance now being described, a closed bottom.

It will be understood, however, that the shape of the tube bottom may be varied as desired depending upon the shape of the lower end I8 of the plunger and the shape of the bottom portion of the die cavity. For example, in Fig. '7, I have shown the lower part of the wall I9 of the die cavity as being in the shape of a frustum of a cone and the end part 2&3 of the male die as correspondingly shaped.

In Fig. 4, the male die is provided with a projection 2i of the desired diameter which projection is intended to enter the opening 22 communicating with the die cavity and thereby to form a readily severable portion 23 which when later cut oi leaves the bottom of the tube 24 completely or partly open as desired. Other desired forms of the lower die-formed end portion of the resulting tube may be readily produced merely by varying the shape of the die cavity and the shape of the lower end of the plunger as will now be readily understood and need not be further described.

However, an important feature of the invention is the diversion, expansion and control of that portion of the metal of the slug I1 which flows upwardly out of the die cavity and around the plunger1 l. By so controlling and diverting the upwardly flowing metal within the limits of the ductility of the metal, a great variety of sizes and shapes on different portions of the lengths of the resulting tube may be produced. In the form of the invention shown in Figs. 1 and 2, I prefer to control and divert the upwardly flowing excess metal by means of a suitable sleeve '4 as 25 adjustably secured to the plunger I0 at any point of the length of said plunger as by means of one or more set screws 26. By adjusting the position of the sleeve vertically, the relative lengths of the expanded and unaltered portions of the tube are determined. The sleeve 25 is slidably and closely fitted to the plunger and may take a variety of dilerent forms. In the form shown, the lower cylindrical portion 2l of the sleeve terminates in a lowermost bevelled or conical edge portion 28. At its upper end, the sleeve is enlarged as at 29 to provide enough material for the proper operation oi the securing means.

It will be understood, however, that if desired, the sleeve may be formed integrally with the plunger. I prefer to make the sleeve separate for purposes of economy, since the same plunger may be used with sleeves oi dilferent sizes or shapes and each sleeve may be adjusted vertically when it is desired to change the relative lengths of the different tube portions.

As shown in Fig. 2, the metal flowing out of the die cavity is irst given the smaller cylindrical shape determined by the lower end portion lil or" the plunger and the shape of the die opening and ows in a predetermined vertical path but when said metal reaches the bevelled part or shoulder 28 of the sleeve, it is diverted from its normal path of iow and forced to move along said bevelled edge and in a dierent path thereby expanding the diameter of the upper path of the tube thus formed to the diameter of the portion 2l. Since the metal resists expansion after it reaches the upper corner 3l) of the bevelled portion, the inherent tension therein resisting expansion causes the metal to change its direction of flow again and to hug the wall 2 thereby producing the enlarged cylindrical portion 3l on the upper part of the tube.

It will thus be seen that by a single extruding operation and by the use of the sleeve 25 or of a correspondingly shaped plunger, it becomes possible to extrude in a single operation a tube having two diferent diameters at different portions of its length. That is, the lower portion 32 of the tube may be made cylindrical and of a given smaller diameter while the upper portion 3l of the tube may also be made cylindrical and of a larger diameter, said portions being joined by the conical portion 33. After the plunger has been raised out of the female die, the resulting thin-walled hollow article is discharged from the plunger by the air blast through the passage H.

The thus extruded tube may be readily finished on another machine by trimming it to the proper length and forming the portion S3 into the exact right-angled shape desired. An additional operation such as threading or the like may also be performed in a manner and by means well known in the art. For example, in Fig. 3, I have shown the trimming and forming roller 35 provided with the trimming tool 35 for cutting the tube to the required length and also provided with the forming tool 3l for accurately forming the corner portion 38 to the exact shape desired while the tube is mounted on the suitable revolving mandrel 39.

It will be understood that the method hereinbefore described, that is, the extrusion of a tube having different diameters from a slug in a single operation is not limited to the formation of cylindrical portions on the tube but numerous other shapes may be given to the tube. For example, in Fig. 5, I have shown the male die lil provided with a sleeve Il@ having a beaded exterior surface 4I to replace the cylindrical surface 2l. I have @andere foimdthatithe owingtor V.eitrudedfexcessfmetal iowmg'tolitsinternal tension'rhugsthe surface Al itand fproduces .'a correspondingly beaded upper lportionron theltub'e and doesnot continuefflow- 'ing in theI direction; of/.theinclined shoulder 1.28.

In 6,' I havefshown-the cylindricallportion 'i2-l o'f-thesleeve replaced byfthe hexagonal -por- Ttion il? thereby .to1produce a thin-walled upper Yportion onl the tiibeLliexagonaLincross-section" and -v` slightly'larger if desiredithan= thev cylindr-icalportion 32 of the tube.

- Other imodications lof the formation 'ofi-the Walls of thefsleeve willlbesobV-ious inf connection swith =the formationof yterminal edge portions on fthe Jv'extruded tube of other. shapes #and designs. llt Ju/ill also Ybe .understood Ithat sby .makinglithe `5`lc'eadsli I- concave instead ofconvex'fa/iiuted upper 'end will-be obtained ion-'the 'tubein amanner `which will now be obvious. Y

--Nor-is myinventionflimitedLto the formation eofcylindrical. lower. portions-on-.the tube. Forv ex- -ample, in Fig..8, .I have' shown ktheglower end'i :'offthe male` die-of hexagonal .cross-section, thedie cavity .5i v.being correspondingly .made of .hexagonallcrossesection. .The sleeve.,2,;however,.has been imade cylindrical. :.Consequently, when the itubeis extruded, the lower portion .53 thereof is Lof heXagOnal.crossesection determined i'by the llowerr portion. oftheplungerwhile theupper .poriteniof the tube.. is .ofzcircular cross-*section and :cylindrical as determined by Lthelshape of. the sle'evell52- As shown in Fig. 7, the lower portion .55;offthe tubeis cylindrical .while :the upper portion 5S .thereof is .of .hexagonal .cross-section :as tdeterfmine'd by .the hexagonal shaperof `the vsleeve 51 which .is similar to the sleeve 2. Thedie-:formed -l'ower endof the tubewis-here shown-fasuconical .tforpurposes .of illustration.

.Itwillnowbe understood that` .by varying-.the-v :ishapefof .the surface of the sleeve, anysrequired fshaperand diameter .within the limits of .ductility "ofthe metalzmay beipreduced. Thatfis, anypy- "ramidal vor;p--"isrnatic tubeA of-reguiar or: irregular .polygonal'crcs v-cectiornmaybe `producedfas Well as :.any cylindrical tube .of regular` or .irregular I'curved cross-.sectional shape. When the sleeve .surface is made .eccentric tothe surfacefof .the plunger, eccentric upper partsV may vbe .correspondingly producedvonv the extrudedntube. The "lengths of theextruded lower portion 32y and of fthe upperportion mayreadily. be .Y controlled and determined by shifting the-sleeve 25 vertically in the proper direction. on the'plunger. It -will furtherbe understood that bythe use'zofad- .ditional shoulders or-Jbevelledportions '28 yonthe .sleeve andadditionalfsurfaces ofthe diameters diferentfrom thesurface 2l, tubes havinglmultiple crmore than two .different diameters yand 1.inf fact. any number of different diameters within -the limits of expansibility of the metal can :be iproduced. I have found, however, that the shoul- .-ders. connecting the different surfaces of thesleeve and leading from the lateral surface of the .plungerto vthat ofthe sleeve should be. arranged ,.preferablyat an obtuse angle to the adjacent sur- .faces .between which they are arrangedso as-to .change the direction of .now of the metal with as little abruptness as possible unless aiiared, beaded, curledor serrated edge is desired. `Byen- .larging orreducing they diameter of theportion "2! ofthe male 'die l(Fig. 4) or plunger, casings, 'shells or tubes having completely open endskmay be'produced, thetube"being finishedby a knockfro . Itr iwill'rbe iunderstood fthatxthe'term .tube :as ulsedlfherein .is iintend'ed .to .includefany v.compara- Itively Lthin-walled :hollowi article .regardless of .its ssh'ape. and .the :number f: ofV .different :diameters rtherein orlwhether one endiis closedor open,;3or whether xsaid' end iis :provided @with Aa :neck .ora lithi'cinenediportion.oriwith lugs orzprojections of .various.L sorts'and ..typ es for :different purposes.

:It iw'ill .thus @be .seenfithat .I shave .provided ia simplebut.commercially practicalniethod for ex- ;truding-inoncpperation froma sluga multiple -diametertube Shaving .any .regular or irregular :polygonal ,or curved .perimeter .and having any :desired type kof edge such as curled, flared, 1 serirated and the likeand having .anyltype .ofzdie- :formed openorclosed end thereon.

It WillLalso rbeseen that I haveprovided simple but..'e`iiicient.rneans forcarrying out the method described herein .andfurtherfthat I have provided La newtubezformedfinpne operationfrom a-slug :and1:of.:multiple diameter and/or .of diierent cross-.sectional shapes.

fWhile .Lhaveshown and described. certain spe- .cicembodiinents'of my invention, I donot .wish .to :lee-.understood I as .limiting myself thereto, .but aintendtoLclaiin theinventionaslbroadly as may :.be'lpermitted by.z the: state; of :the priortart andthe scope of the appendedfclaims.

1. In apparatus for the impact 'extrusion of fhollow; :soft .metal articles .in .one operation and .including Va 'plunger having lan end vportion adapted to enter into and cooperate with a female :die anda remaining portion at all .times ar- `range'dfbeyond the femaledie, means for con- .'troiling and diverting -'metalflowing out ofthe female die in -soiid formfaxiallyv along theplunger `at high speed under high axialpressure Vand in r'a'formative stateffrom the normal direction imparted theretoV by the plunger and the die, said .means comprising. a sleeve surrounding re- "maining portion oit-the plunger and adjustablyv imfountedf there-cn.

A-napparatus or"extru,ding holioiv articles vfrom-fafmetal slug inone operation,aplunger `having an end-portion adapted to enterY and to -cooperate with a sh-allow Vfemale die to form one end'part-of an article-a sleeve on the remaining portion of the plunger substantially instantaneouslyto'divert' thaty part of the metal of the 'slug xiiowin-gpast said end portion of the-plunger at high-speed andina formative state, and means fora'djustably securing the sleeve tothe plunger.

`.3."The method of producinga one-piece tube 'having a'lovver die-formed part, a first body part "of airst predetermined uniform cross section, a secondbody part having a second predetermined luniformcross section differentl from the first cross l'section and a substantiallyl conical part joining theffirst and second body` parts, said body lparts 'having thin walls loa-thickness approximating `the thickness ofthe walls'of conventional collapsible metal *tubes and'conventional'cans of corresponding diameter, said method comprising placing wholly within a'female die an unheated non-ferrous disc slug of metalv extrudable at room 'temperature with the upper surface of the slug below the top of the die thereby to leave at least the-upper part of thedie empty of slug metal, --striking the-slug a single` rapid blow'by rapidly Vmoving apunch into the die first to initiate the sdie-'forming of the slug into"the'die-formed part 'of thetube 'by the 'downward pressure of the punch fon :the'slug before'any `extrusion of slug outpperationon 'theweakenedlower'end' thereof. 75 metaloutof theuienccurs,"therebyto movepart of the slug metal into positionV to fill the empty space between the punch and the die, second to extrude the excess part of the slug metal thus moved out of the die, by moving said metal in a first straight line path, said path being of substantial length corresponding to the length of said first body part and being parallel to the direction of movement of the punch, while continuing the die-forming of part of the slug Within the die until just prior to the final downward movement of the punch, and nally completing the die-forming operation while simultaneously completing the extrusion of the remaining excess of slug metal out of the die and also simultaneously stretching a predetermined length of the upper' part of the tube by moving said length through an angular relatively short path non-parallel to said first straight line path, thereby radially stretching successive parts of said predetermined length rst to a substantially conical shape corresponding to the shape of said substantially conical part of the tube and then to said second predetermined cross section as the various parts of said predetermined length move past a given portion of the punch, the metal moving in a straight line path parallel to and spaced outwardly of the rst straight line path free of radial stress after the metal passes said portion of the punch.

4. The impact extrusion method of producing a two-diameter thin-walled elongated metal tube by the action of an extrusion punch and die upon an unheated disc slug of extrudable metal placed entirely within the die, said tube having a dieformed lower end part, an extruded upper end part of uniform circular cross section and an extruded intermediate part of a smaller uniform circular cross section, said method comprising forming the end die-formed part of the tube between the die and the punch, forming the intermediate part of the tube solely by extrusion of the slug out of the die and axially along the punch, and forming the upper part of the tube by continuing the extrusion of the slug along the punch combined with radial stretching of the upper part of the tube within the limits of the ductility of the metal as the various portions of said upper part move firse obliquely past a predetermined part of the punch and then freely axially of the punch.

5. The method of producing a thin-walled elongated tube having a die-formed lower end part, an extruded upper end part of uniform cross section, and an extruded intermediate part of a uniform cross section diierent from that of the upper end part, said method comprising placing an unheated slug of non-ferrous metal extrudable at room temperatures wholly within a die with the upper surface of the slug below the top of the die, moving a punch downwardly into a cooperating die and then into the slug a distance less than the depth of the die, and, during the initial part of the movement of the punch into the slug initiating the die-forming of the end part of the tube by the downward pressure of the punch on the slug before any extrusion of the slug metal out of the die occurs, continuing the die-forming of the lower end part of the tube and simultaneously extruding the slug metal in excess of the dieformed part of the tube axially of and around the punch and out of the die along an initial path of substantial length to form the intermediate part of the tube partly within` and partly above the die, stretching the leading end part of the metal extruded out of the die along a predetermined portion of the upper end of said initial path in substantial upward spaced relation to the fclie at all times to divert the flowing metal progressively into an angular path non-parallel to the initial path, and freeing the owing metal at the uppermost end of said angular path from stretching stresses thereby to permit the uppermost part of the metal to flow in a final path parallel to the initial path and to assume the stretched shape of the upper part of the tube permanently and progessively along said upper part until downward movement of the punch ceases.

6. The impact extrusion method of producing a thin-walled elongated tube having a dieformed end part, an extruded and stretched upper end part of a first uniform cross section and an extruded intermediate part of a different uniform cross section, said method comprising initiating the die-forming of an unheated nonferrous slug at room temperatures by impact extrusion at high speed, completing the dieforming while simultaneously extruding the slug into a tube of uniform cross section corresponding to said diierent cross section while the tube is being lengthened during the extrusion operation, and continuously stretching the upper part of the tube progressively and uniformly to said first cross section by interposing an obstruction in a relatively short length of the path of the slug metal at a selected point below the end of the path of the leading end edge of the extruded metal and at the upper end of the path of the intermediate extruded and unstretched part of thetube.

7. The punch and die impact extrusion method of producing a thin-walled tube having a die-formed part, a rst body part having a predetermined uniform cross section, and a second body part having a second and different predetermined uniform cross section, said method 4 comprising the performance of a simultaneous die-forming, extruding and radial stretching operation upon an unheated disc-like slug of extrudable non-ferrous metal placed wholly within the die to form the metal first to leave the die into a tube part corresponding in cross section to said predetermined cross section and, while said metal moves past a predetermined part of the punch which is at all times in upward spaced relation to the die, expanding the tube part to said second cross section.

8. The impact extrusion method of claim '7 wherein one of the body parts of the tube is of circular cross section and the other body part is of polygonal cross section.

9. The method of producing a tube having relatively thin walls of the thickness approximately of conventional cans and shells of the same diameter as the tube and having one wholly extruded portion thereof of a uniform cross sectional shape diierent from that of another wholly extruded portion of the tube, said method comprising producing the tube from an unheated shallow disc slug of non-ferrous extrudable metal by impact extrusion in a single operation by rst placing the slug wholly within an impact extrusion die and then striking the slug a blow with an impact extrusion punch to cause the metal of the slug to ow in a straight line path in a given direction along the punch for a sufcient distance to form the first mentioned portion, and diverting and controlling the flow of the leading portion of the extruded metal from the given direction by the punch to an angular direction for a predetermined relatively. short path to stretch said leading portion within the limit of ductility of the unheated metal, and nally to a straight line path parallel to and spaced outwardly and upwardly of the first mentioned straight line path during the extrusion flow of the metal to form said second mentioned portion.

10. In the impact extrusion method of making a thin-walled elongated tube wherein the metal of a cold slug wholly within and below the top of a die is extruded by causing the metal to flow out of the die along a path of substantial length in a vertical direction, the step of changing the direction of ow of that part of the Cil metal rst to leave the die from the vertical direction to an inclined direction through a relatively short path after said part has flowed in the given direction for a suiicient distance to form the greater part of the length of the tube, said step stretching the metal first to leave the die progressively as said metal passes a given point and then releasing the metal from stress past said point to permit the metal to ow again vertically to form an upper tube part of predetermined uniform cross sectional shape.

11. In the impact extrusion method of making a tube from an unheated slug wholly within a die and of insuicient size to ll the die, in one operation, the step of first initiating the dieforming of one end part of the tube by spreading the slug to ll the die and, during the progress of the die-forming operation, axially extruding excess slug metal out of the die to form progressively a substantial length of an intermediate part of the tube, progressively expanding the other end part of the tube as said other end part moves past a given point, and releasing said other part from radial stress after it has passed said point.

12. In the impact extrusion method of making a thin-walled elongated hollow article from an unheated shallow disc-like slug of cold extrudable metal in one operation, die-forming one end part of the article while the slug is wholly within a die and, while extruding the slug to form the thickness of the remainder of the article to approximately the least thickness permitted by the speed of the operation and the ductility of the metal, expanding the other end part of the article as the metal thereof passes a given point during the extruding operation by interposing an obstruction of predetermined shape in the path of ow of the thinned extruded metal at said point to divert the ow to a different relatively short path thereby to stretch said other end part within the limit of ductility of the metal, and releasing said other end part of all radial stress thereon after it has passed the obstruction.

13. The method of claim 11 and after the outermost portion of said other end part has moved a predetermined distance free of stress, expanding a predetermined portion of said other end part a second time in substantially the same manner as said portion was first expanded.

HAROLD F. TEMPLE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 716,466 North Dec. 23,1902 1,024,840 Ehrhardt Apr. 30, 1912 1,702,278 Simons Feb. 19, 1929 1,771,620 Ehrmann July 29, 1930 1,968,792 Yeomans July 31,1934 2,023,879 Friden Dec. 10,1935 2,096,245 Heinze et al. Oct. 19,1937 2,162,776 Friden June 20, 1939 2,176,364 Skinner et al. Oct. 17,1939 2,225,902 Cartwright Dec. 24,1940 2,241,091 Hood May 6,1941 2,244,954 Lenz et al. June 10,1941

FOREIGN PATENTS Number Country Date 128,271 Great Britain June 26. 1919 

